As oil and gas wells age their production often decreases. While a portion of such diminution is the obvious result of depletion of the hydrocarbon reservoir which is being tapped, the decrease of flow is often the result of the collection of higher weight hydrocarbons, such as paraffins in and near the bore hole and in the fractured hydrocarbon-bearing ground formation, which inhibit the hydrocarbon flow. In addition, the introduction of chemicals into the borehole for a variety of desired effects can, over the long term, cause flow blockage. In a similar manner, hydrocarbon pipelines may collect deposits which, over the long term, diminish the effective inner diameter of the pipe and thus limit its flow capacity.
A variety of techniques are known and have been applied to remediate such blockage conditions. These techniques include mechanical procedures, such as scraping, the introduction of further chemical treatments to react with and dissolve blockages, as well as, more recently, the application of sonic energy to attack the blockages. Each of such techniques have their advantages and disadvantages.
It is known to utilize hydrogen peroxide (H2O2) as a stimulation vehicle. As an active oxidizer, the direct injection of hydrogen peroxide into a well serves as a chemical reactant. Because of its high reactivity, however, the injection of hydrogen peroxide into a well is fraught with difficulties and potential hazards. In addition, ever-tightening environmental standards preventing the discharge of hazardous materials into the environment further mitigate against the direct injection of hydrogen peroxide.
It is also known to use hydrogen peroxide as a decomposition agent. The decomposition products of hydrogen peroxide are water and oxygen. The decomposition of hydrogen peroxide by use of an appropriate catalyst generates a high temperature mixture of oxygen and water in the form of water vapor or steam, and the injection of such a mixture into a well has found some measure of commercial value. As decomposition products, both oxygen and water can be vented to the environment without the environmental risk or harm associated with other agents.
U.S. Pat. No. 3,235,006 to Hujsak discloses the direction of hydrogen peroxide into a well pipe. A catalyst is located within the well at the lower end of the pipe. Upon contact with the catalyst the injected peroxide decomposes, the decomposition products performing a stimulation treatment. Such methodology requires care to keep the peroxide free of potential reactants as it is delivered down the piping. The decomposition reaction is also difficult to monitor and is uncontrolled. U.S. Pat. No. 4,475,596 to Papst utilizes a similar system in which a decomposition reaction is initiated within the borehole at or above the level of the formation to be treated.
U.S. Pat. No. 4,967,840 of Nov. 6, 1990 to Miller discloses an apparatus for decomposing hydrogen peroxide especially for use as a flow stimulation media for hydrocarbon-bearing formations and discloses a basic system and method for its use in association therewith, in which the decomposition is performed outside the well, and the reaction products directed into the well. As the introduction of any stimulation product into a hydrocarbon well must be carefully controlled and monitored, however, the '840 patent is deficient in that it neither provides an apparatus for efficient control or generation of the decomposition products, nor allows supervision or control over the metering of the decomposition products into a well or other facility.
It is accordingly a purpose of the present invention to provide a method and apparatus for performing a decomposition reaction for hydrogen peroxide outside a well or other structure to which the decomposition products are to be introduced and utilizing the decomposition products in connection with well stimulation and pipeline cleaning.
A further purpose of the present invention is to provide such an apparatus which allows the decomposition reaction to be controlled, monitored and adjusted in an efficient and ongoing manner.